High Limit Switch (E.c.o.); Dishwashing Machine Requirement; Circulating Pump; Installation Instructions - A.O. Smith CYCLONE XHE BTH 300A Installation & Operating Instructions Manual

The temperature may be adjusted from 80°F/27°C to 180°F/82°C.
The thermostat was adjusted to 120°F/49°C before the heater was
shipped from the factory. It is recommended that lower water
temperatures be used to avoid the risk of scalding. It is further
recommended, in all cases, that the water temperature be set for
the lowest temperature which satisfies your hot water needs. This
will also provide the most energy efficient operation of the water
heater and minimize scale formation.
SETTING THE WATER HEATER TEMPERATURE AT 120°F/49°C
WILL REDUCE THE RISK OF SCALDS. Some states require
settings at specific lower temperatures.
Figure 1 shows the approximate time-to-burn relationship for normal
adult skin. Short repeated heating cycles caused by small hot water
uses can cause temperatures at the point of use to exceed the
thermostat setting by up to 20°F (11C°). If you experience this type
of use, you should consider using lower temperature settings to
reduce scald hazards.
Temperature
Setting
180°F / 82°C
170°F / 77°C
160°F / 71°C
150°F / 66°C
140°F / 60°C
130°F / 54°C
120°F / 49°C
Valves for reducing point-of-use temperature by mixing cold and
hot water are available (see Figure 2). Also available are inexpensive
devices that attach to faucets to limit hot water temperatures.
Contact a licensed plumber or the local plumbing authority.

HIGH LIMIT SWITCH (E.C.O.)

The top immersion well of the dual bulb controller also contains
the high limit (energy cutoff) sensor. The high limit switch interrupts
the main burner gas flow should the water temperature reach
approximately 202°F/94°C.
Should the high limit switch activate, it must be manually reset by
depressing the Temperature Adjustment Button/Reset Button on
Time to Produce 2nd & 3rd
Degree Burns on Adult Skin
Nearly instantaneous
Nearly instantaneous
About 1/2 second
About 1-1/2 seconds
Less than 5 seconds
About 30 seconds
More than 5 minutes
FIGURE 1
FIGURE 2
the display board. The water temperature must drop below 160°F/
71°C before the controller can be reset.
Continued manual resetting of high limit control, preceded by higher
than usual water temperature is evidence of high limit switch
operation. The following is a possible reason for high limit switch
operation.
• A malfunction in the thermostatic controls would allow the gas
valve to remain open causing water temperature to exceed the
thermostat setting. The water temperature would continue to
rise until high limit switch operation.
Contact your dealer or servicer if continued high limit switch
operation occurs.

DISHWASHING MACHINE REQUIREMENT

All dishwashing machines meeting the National Sanitation
Foundation requirements are designed to operate with water flow
pressures between 15 and 25 pounds per square inch (103 Kpa
and 173 Kpa). Flow pressures above 25 pounds per square inch
(173 Kpa), or below 15 pounds per square inch (103 Kpa), will
result in improperly sanitized dishes. Where pressures are high, a
water pressure reducing or flow regulating control valve should be
used in the 180°F (82°C) line to the dishwashing machine, and
should be adjusted to deliver water between these limits.
The National Sanitation Foundation also recommends circulation
of 180°F (82°C) water. Where this is done, the circulation should
be very gentle so that it does not cause any unnecessary turbulence
inside the water heater. The circulation should be just enough to
provide 180°F (82°C) water at the point of take-off to the dishwashing
machine. Adjust flow by means of the plug cock in the circulating
line. (See installation diagrams.)

CIRCULATING PUMP

A circulating pump is used when a system requires a circulating
loop or there is a storage tank used in conjunction with the heater.
Refer to the piping diagrams at rear of manual for electrical hookup
information and install in accordance with the latest version of the
National Electric Code ANSI/NFPA No. 70 or Canadian Code CSA
C22.1.
All bronze circulators are recommended for used with commercial
water heaters.
Although circulators are oiled and operated by the manufacturer
some circulators must be oiled again before operated. Please refer
to manufacturer's instructions.

INSTALLATION INSTRUCTIONS

REQUIRED ABILITY

INSTALLATION OR SERVICE OF THIS WATER HEATER
REQUIRES ABILITY EQUIVALENT TO THAT OF A LICENSED
TRADESMAN IN THE FIELD INVOLVED. PLUMBING, AIR
SUPPLY, VENTING, GAS SUPPLY AND ELECTRICAL WORK ARE
REQUIRED.

INSULATION BLANKETS

Insulation blankets available to the general public for external use
on gas water heaters are not approved for use on your A.O. Smith
water heater. The purpose of an insulation blanket is to reduce the
standby heat loss encountered with storage tank water heaters.
Your A.O. Smith water heater meets or exceeds the ASHRAE/IES
90.1b 1992 standards with respect to insulation and standby loss
requirements, making an insulation blanket unnecessary.
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